The invention relates to a foil in the form of an elongate film strip with edge perforations and conductor tracks which serves as a carrier for a plurality of integrated circuits to be incorporated preferably in chip cards, the conductor tracks being cut out from a metal foil and glued onto a synthetic foil provided with holes or openings.
Foils of this kind are generally known and serve to minimize the complexity and hence cost of manufacture of chip cards. Because the foil is formed as an elongate film strip with a periodic configuration of the same conductor track pattern, the integrated circuits can be deposited and contacted by means of an automatic apparatus. Subsequently, the integrated circuits with the surrounding conductor track pattern are cut out from the film strip as one unit so as to be incorporated in the appropriate parts of the chip cards. The conductor track pattern at the same time serves for the contacting of the integrated circuit from outside the chip card.
Since recently integrated circuits are known which can be operated not only via contacts but also in a contactless manner, that is to say inductively via a coil. This coil is separately incorporated in the chip card and connected to the separate terminals of the integrated circuit. This connection can be realized by connecting the ends of the coil directly to appropriate terminals of the integrated circuit. Such a connection, however, has various drawbacks; notably the integrated circuit is then severely loaded from a mechanical point of view so that it could be damaged.
Another possibility consists in providing a further metal foil with an appropriate conductor track pattern on the synthetic foil, so that the synthetic foil is covered with a conductor track pattern on both sides, one conductor track pattern serving only to establish a connection between the coil and the integrated circuit. However, it has been found that such a synthetic foil with conductor tracks on both sides is much more rigid than a foil of this kind which is provided with conductor tracks on one side only, so that it cannot be readily handled by the customary automatic apparatus or gives rise to disruptions during operation.
It is an object of the invention to construct a foil in the form of an elongate film strip provided with edge perforations and conductor tracks of the kind set forth in such a manner that it is suitable to accommodate integrated circuits which can be operated via contacts as well as in a contactless manner, the film strip nevertheless remaining as flexible as possible.
This object is achieved according to the invention in that a respective metal foil with different conductor track patterns is glued to each side of the synthetic foil, and that the metal foils on both sides comprise, in addition to the specified conductor track pattern, interruptions in order to achieve a significant reduction of the overall cross-section of both metal foils at short intervals in the longitudinal direction of the foil strip, perpendicularly to the longitudinal direction of the film strip.
As a result of the reduction of the cross-section in both conductor tracks, the film strip remains so flexible in the longitudinal direction that it can be readily handled by contemporary automatic apparatus without causing significant disturbances. The fact should be taken into account that the dimensions and the shape of the conductor tracks in the contact field, via which the integrated circuit is driven by way of contacts, are predetermined to a high degree. Moreover, in the case of a conductor track pattern which is cut out from a metal foil and subsequently glued onto a synthetic foil each part of the conductor track must be connected to the other parts. This also holds for a subsequent surface enhancement of the conductor tracks. However, via appropriate configuration it can be ensured that connections in the conductor track pattern extend essentially transversely of the longitudinal direction of the film strip, so that the conductor track pattern can be provided with interruptions which reduce the overall cross-section of both metal foils perpendicularly to the longitudinal direction of the film strip each time at short intervals.
In order to achieve a defined position on the synthetic foil during the gluing on the metal foil with the cut out conductor track pattern, the synthetic foil as well as the metal foil is provided with edge perforations which are used for alignment. The edge strip of the two metal foils with the edge perforations, however, leads to increased rigidity in the longitudinal direction of the film strip. In order to reduce such rigidity, in a further embodiment of the invention both metal foils are provided, at corresponding locations at the area of the edge perforations, with an opening which extends over a plurality of successive edge perforations. It has been found that it suffices to perform alignment on the basis of a few edge perforations only, notably on the basis of a respective edge perforation for each conductor track pattern associated with an integrated circuit.
If, instead of the described approach, a further version of the alignment procedure is used which utilizes every edge perforation, it may be advantageous; when the foil according to the invention is conceived accordingly, to provide an opening in at least one metal foil at the area of the edge perforations, which opening extends between every two successive edge perforations but does not contact the edge perforations. It may then suffice when only one of the two metal foils is provided with said openings at the area of the edge perforations. A particularly high flexibility is obtained, however, by providing both metal foils, in corresponding locations at the area of the edge perforations, with openings which extend between each time two successive edge perforations but do not contact the edge perforations.
These embodiments of the foil according to the invention offer advantages, notably for the manufacture of chip cards, when all edge perforations are used for the optical centering of the foil during its mounting in the chip card. In that case it is advantageous when all edge perforations are uniformly bordered by parts of at least one of the metal foils. However, when edge perforations with borders of metal foil as well as edge perforations with borders of merely synthetic foil are used for the optical centering of the foil, the different optical transparency of the edge perforations and their borders must be taken into account in the case of automatic centering. The latter embodiment of the foil according to the invention creates circumstances which can then be particularly simply controlled.